The present invention relates generally to an encapsulated glazing product including a glass substrate having a layer of plastic material secured thereto and presenting an exposed surface, and a polymeric frame member surrounding a major portion of the peripheral regions of the glass and plastic layer assembly.
In the early stages of the automobile industry, single sheets of ordinary or annealed glass were employed as windshields. As it became evident that this type of windshield presented a considerable safety hazard, the single sheets of annealed glass were replaced with single sheets of heat treated or tempered glass. Thereafter, as laminated safety glass was developed to reduce the severity of lacerative injuries, its use in automobile windshields greatly increased until today, when almost all automotive windshields are constructed of some type of laminated glass. However, the use of laminated glazing structures in all of the openings of automotive vehicles, besides being very costly, can substantially add to the weight of the vehicle thereby adversely affecting fuel economies which are of great importance at the present time. Therefore, with a mind for developing as safe a vehicle as possible within acceptable weight parameters, attention has been given to developing anti-lacerative glazing structures for automotive vehicles. The major thrust of the present invention is directed to glazing structures for use in vehicles which structures have inherent safety characteristics and are nevertheless of a reduced overall weight. It is felt to be advantageous to retrace the history of vehicular glazing structures which are hereinafter briefly addressed.
Today, typically, an assembly of laminated glass of the type utilized in vehicle windshields consists of two sheets of glass bonded together with a thin plastic interlayer, such as a sheet polyvinyl butyral, for example. In the event of an impact on a laminated glass windshield sufficient to break the glass, the plastic interlayer functions to bind the glass fragments together, thus reducing the risk of injury to a driver or passenger as a result of flying glass or contact with the windshield. Further developments with this type of laminated glass, such as those disclosed in U.S. Pat. No. 3,231,461, have resulted in laminated windshields with improved penetration resistance. Consequently, in view of the ever growing recognition of the necessity for increased safety precautions, continuing efforts have been and are still being made to appreciably reduce the injury producing potential of an automobile windshield.
Recently, it has been found that the addition of a second plastic layer bonded to the exposed surface of the inboard glass sheet of the laminated windshield further increases the safety effectiveness of the windshield. The second plastic layer has typically been termed a protective laceration inhibiting shield since it has been found that the additional plastic layer will appreciably reduce the number and severity of lacerative injuries to persons thrown against the windshield under all impact conditions. Further, it has been found that the laceration shield when produced under certain conditions of manufacture improves the ability of the laminated windshield to decelerate the movement of a person thrown against the windshield, while also increasing the penetration resistance of the windshield as compared to conventional laminated windshields. Also, the laceration shield reduces the amount of flying glass and, thus, the injury to occupants as a result of objects that may be thrown against the windshield from overpasses or elsewhere outside the vehicle.
An example of an automotive windshield which incorporates, as part of its laminated structure, a protective laceration shield bonded to its inboard glass surface is disclosed in U.S. Pat. No. 4,242,403. In this patent, the laceration shield includes a penetration resisting multi-layer body consisting of an inner layer of relatively soft, extensible plastic material such as polyvinyl butyral, for example, which is adhered to the inboard surface of the windshield, an intermediate layer of more durable plastic such as a polyester, and an outer coating of an abrasion resistant material.
It will be understood that an unlaminated glass sheet could be provided in thickness sufficient to preclude shattering. However, such a glass product would not be acceptable to the automotive industry because it would result in a part employing too much weight.
While automotive safety standards in the United States require laminated structures for windshields, side lights and backlights may be fabricated of single glass sheets which are tempered. Since, in a rather substantial number of vehicle collisions, occupants are caused to be propelled through side lights, continued attention must also be given to the safety considerations of the construction of side light and back light structures.
It has been found that a thinner glass part may be produced from a combination of a sheet of glass and a plastic layer to provide a lighter weight product having acceptable scratch and shatter resistance properties. Assuming that the appropriate bonding is achieved between the glass and plastic sheet, the product will shatter in many small pieces of glass, a larger portion of which will tend to cling to the plastic with obvious safety effects.
An important aspect of the design of a glass-plastic product for use in the automotive industry is the manner in which such products absorb energy upon the impact of the type experienced during an automobile collision. It is a desideratum of the designers to develop a structure for use in vehicular applications which will absorb the energy upon impact on a curve which minimizes injury to automobile occupants.
It has been found that one method for applying a plastic layer to one surface of a single sheet of glass is disclosed in U.S. Pat. No. 3,806,387. In this method, a sheet of glass, a layer of adhesive, and a layer of thin transparent plastic sheeting are assembled in a stack to produce a laminated assembly. A second sheet of forming glass conforming to the configuration of the sheet of glass in the laminated assembly is then placed on top of the plastic sheet. The surface of the glass forming sheet which is placed adjacent to the plastic sheet is coated with a demolding agent to prevent any adhesion between the glass forming sheet and the plastic sheet. Next, the spaces between the individual lamina are evacuated and the laminated assembly is positioned in an autoclave. The autoclave applies pressure to the exterior surfaces of the laminated assembly while heating the assembly to a temperature which causes bonding between the glass sheet and the plastic sheet. After the assembly is removed from the autoclave, the forming sheet can be removed from the stack.
The structures and methods of producing the structures of the prior art have failed to fully contemplate the necessity for producing anti-lacerative glazing structures which can be used in side light, back light and sun roof applications as well as for windshield applications.
The present invention contemplates an anti-lacerative glazing structure and method of producing the same which cooperate to increase the safety levels of vehicular glazings within acceptable economic and weight parameters.